This present disclosure relates to the field of medical devices, and more particularly, to devices such as sheaths, catheters, or tubes with a mechanism to secure a braided filament.
Numerous advances of considerable note have occurred in medical surgical techniques over the last few decades. Among the most significant advances has been the adoption, and now-routine performance, of a wide variety of minimally invasive procedures. Non-limiting examples of such procedures include angioplasty, endoscopy, laparoscopy, and arthroscopy. These minimally invasive procedures can be distinguished from conventional open surgical procedures in that access to a site of concern within a patient is achieved through a relatively small incision, into which a tubular device (or tubular portion of a device) is inserted or introduced. The tubular device, or device portion, keeps the incision open while permitting access to the target site via the interior (i.e., lumen) of the tubular device. Body passageways in which medical interventional devices are now commonly introduced include the esophagus, trachea, colon, biliary tract, urinary tract, and vascular system, among other locations within the body. One particularly significant example of a minimally invasive technique involves the temporary or permanent implantation of a medical interventional device, such as a stent, into a passageway in the body of a patient.
When placing the medical interventional device, communication with the passageway is typically attained by inserting an access device, such as an introducer sheath, into the body passageway. One typical procedure for inserting the introducer sheath is the well-known Seldinger percutaneous entry technique. In the Seldinger technique, a needle is initially inserted into the passageway, such as a vessel, and a wire guide is inserted into the vessel through a bore of the needle. The needle is withdrawn, and an introducer assembly is inserted over the wire guide into the opening in the vessel.
Typically, the introducer assembly includes an outer introducer sheath, and an inner dilator having a tapered distal end. The tapered end of the dilator stretches the opening in the vessel in controlled fashion, so that introduction of the larger diameter introducer sheath may then be carried out with a minimum of trauma to the patient. Following satisfactory placement of the introducer sheath, the dilator is removed, leaving at least the distal portion of the larger diameter introducer sheath in place in the vessel. The interventional device, such as an expandable stent, etc., may then be inserted through the introducer sheath for placement at a target site within the vasculature. Alternatively, the stent may be placed at the target site by withdrawing the introducer sheath from around the constricted stent. In either technique, upon placement at the target site, the stent expands to the diameter of the vessel.
Historically, percutaneous insertion techniques were problematic, due at least in large part to the lack of flexibility and/or kink resistance of the sheath. Early sheaths were typically formed of a relatively stiff fluorocarbon, such as polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP). The sheaths were typically of thin-walled construction, and were prone to kinking, particularly when threaded through tortuous pathways within the body. Increasing the thickness of the sheath only minimally improved the kink resistance of the sheath. At the same time, the added thickness occupied valuable space in the vessel, thereby minimizing the diameter of the interventional device that could be passed therethrough. In addition, increasing the thickness of the sheath necessitated the use of a larger entry opening than would otherwise be required.
A kinked sheath is essentially unusable, and generally cannot be straightened while positioned in the body of the patient. Consequently, once a sheath kinks, the sheath must be removed from the vessel, leaving an enlarged, bleeding opening which cannot generally be reused. Access to the vessel must then be re-initiated at an alternative site, and the process repeated with a new sheath. In some cases, a suitable alternative site is not available, and the percutaneous procedure must be abandoned altogether in favor of a different, and often more intrusive, technique.
In recent years, introducer sheaths have been improved in order to enhance their flexibility and kink resistance. Such sheaths are now routinely used to percutaneously access sites in the patient's anatomy that previously could not be accessed with existing sheaths, or that could be accessed only upon the exercise of an undesirable amount of trial and error, with the concomitant discard of sheaths whose placement had been unsuccessful.
Many newer sheaths exhibit a much higher degree of kink resistance than was achievable with prior art sheaths. One example of a flexible, kink resistant introducer sheath is described in U.S. Pat. No. 5,380,304 (“the '304 patent”), which is incorporated herein by reference in its entirety. Here, the sheath described therein includes a lubricious inner liner having a helical coil fitted over the liner. An outer tube is connected to the outer surface of the liner through the coil turns. The coil reinforcement imparts kink resistant to this thin-walled sheath through a wide range of bending.
Another example introducer sheath is described in U.S. Patent Publication No. 2001/0034514 (“the '514 Publication”), which is incorporated herein by reference in its entirety. The sheath described therein is similar in many respects to the sheath of the '304 patent, and is formed such that the proximal end of the sheath has a higher stiffness, while the distal end has a lower stiffness. Since the distal end of the sheath has a lower stiffness (and therefore is more flexible) than the proximal end, the sheath is able to traverse portions of the anatomy that would have been difficult, if not impossible, to traverse with stiffer sheaths. Since the proximal end has a higher stiffness (and is therefore less flexible) than the distal end, the sheath maintains the trackability to traverse tortuous areas of the anatomy. This presence of the coil reinforcement also enables this sheath to be kink resistant through a wide range of bending angles.
Unfortunately, sheaths having a coil can exhibit poor pushability due to axial stretching or compression and exhibit poor torqueability during use. To enhance torqueability and pushability, some introducer sheaths have included a braid, as well as a braid and a coil in the wall of its shaft. Such construction of the sheath is described in U.S. Patent Publication No. 2002/0032408 (“the '408 Publication”), which is incorporated herein by reference in its entirety.
Notwithstanding the benefits that have been achieved by the use of such introducer sheaths, new challenges continue to be faced. For example, during manufacturing of the introducer sheath with a braid, the ends of filaments that define the braid can fray open and poke through the outer layers of the introducer sheath. The ends may also extend inward and poke through the inner liner into the passageway of the sheath. In some instances, the braid filaments will tend to unravel during manufacturing. Consequently, the current processes for controlling the fraying of the braid, such as annealing, still results in many manufacturing rejects.
It is desired to provide an improved introducer apparatus suitable for traversing tortuous passageways in the patient's anatomy, and that is capable of minimizing the problems of the prior art. More particularly, it is desired to provide a braided member configuration within an introducer sheath that is capable of minimizing fraying of the braid end, thereby reducing manufacturing rejects. It would be desirable to reduce the fraying of the braid end without contributing additional thickness to the sheath wall to ensure the sheath wall is as thin as possible.